1. Field of the Invention
The present invention relates to an optical pickup apparatus and, more particularly, to improvements in an inclination angle adjusting mechanism for adjusting inclination angle of an objective lens in an optical pickup apparatus.
2. Description of Related Art
An optical pickup apparatus is typically mounted in an optical disc player apparatus for optical discs such as CD, DVD, and the like. In order to place an optical axis of an objective lens in a direction perpendicular to a recorded surface of the optical disc, the inclination angle of the objective lens may be adjusted. A conventional inclination angle adjusting mechanism for adjusting the inclination angle of the objective lens is described, for example, in Japanese Laid-open patent application HEI 6-195722.
The inclination angle adjusting mechanism described in the Japanese Laid-open patent application HEI 6-195722 has an objective lens mounted on an optical head section. A carriage supports one side of the optical head. A first guide shaft passes the carriage in a sliding manner. The other side of the optical head is supported by a radial-ball bearing that is rotatably mounted on a second guide shaft. The carriage is rotatably mounted with respect to the optical head section about a first axis extending in a tangential direction of an optical disc. A screwed amount of an inclination angle adjusting screw is changed to thereby change an inclination of the optical head about the first axis.
Also, the publication describes an eccentric pin that is rotated to adjust the height of the radial ball bearing that is placed on the second guide shaft. As the height is changed, the inclination amount of the optical head about the first guide shaft can be changed. In other words, the inclination amount of the optical head can be adjusted about the second axis that extends in a radial direction of the optical disc.
The inclination angle adjusting mechanism described above has a first inclination angle adjusting mechanism that adjusts the inclination of the optical head about the first axis, and a second inclination angle adjusting mechanism that adjusts the inclination of the optical head about the second axis that extends in the radial direction of an optical disc. The first inclination angle adjusting mechanism and the second inclination angle adjusting mechanism have different adjustment structures. For example, one of them is provided with the eccentric pin, but the other does not have an eccentric pin. As a result, there are problems in that the number of component parts increases and the structure thereof is relatively complicated.
Also, since the inclination angle adjusting mechanism described above does not have or is difficult to provide a reference point to be used for adjusting the inclination angle of the objective lens, the inclination angle cannot be re-adjusted with good reproducibility. More specifically, the inclination angle of an optical head section may be adjusted before it is shipped out from the factory. However, when the performance of the optical head section has deteriorated for one reason or another, the same condition of the optical head adjusted at the factory cannot be reproduced. Accordingly, it is very difficult to determine or repair such a defect.
For example, in the inclination angle adjusting mechanism of the conventional art described above, reference positions for adjusting the inclination angle are not determined, and thus the apparatus cannot be placed in the reference positions. In other words, the optical head section that has a variety of components mounted thereon is not provided with any reference angle that may be used for mounting the carriage and the eccentric pin that form the inclination angle adjusting mechanism. Therefore, initial inclination angles about various axes of the optical head section that are adjusted when the carriage and the eccentric pin are mounted on the optical head section cannot be reproduced later.
It is an object of the present invention to provide an optical pickup apparatus that solve the problems of the conventional art described above. It is also an object of the present invention to reduce the number of component parts in an optical pickup apparatus and to simplify its structure. Also, it is an object of the present invention to provide an optical pickup apparatus having an inclination angle adjusting mechanism that can readily reproduce the inclination angle.
In order to achieve the above-described objects, in accordance with one embodiment of the present invention, an inclination angle adjusting mechanism has a first inclination angle adjusting mechanism and a second inclination angle adjusting mechanism. The first inclination angle adjusting mechanism is adapted for tilting the objective lens about a first axis that passes through a center of an auxiliary shaft guide groove and extends in a tangential direction of an optical disc. The second inclination angle adjusting mechanism is adapted for tilting the objective lens about a second axis that concurs with a central axis of the main shaft.
The first inclination angle adjusting mechanism has a first bearing shaft for rotatably supporting the main shaft guide frame about the first axis with respect to the main frame, and a first inclination angle adjusting screw that is capable of fixing the main shaft guide frame about the first bearing shaft at a predetermined inclined position.
The second inclination angle adjusting mechanism has a second bearing shaft for rotatably supporting the auxiliary shaft guide frame with respect to the main frame about a third axis that is located between the main shaft and the auxiliary shaft and extends in parallel with the second axis, and a second inclination angle adjusting screw that is capable of fixing the auxiliary shaft guide frame about the second bearing shaft at a predetermined inclined position.
The inclination angle adjusting screws are turned to adjust the inclination angles. Preferably, the inclination angle adjusting screws may not have any plays to accurately perform the adjustment of the inclination angles. For this to be achieved, spring-washers may preferably be disposed between heads of the inclination angle adjusting screws and the guide frames, and the heads of the inclination angle adjusting screws are normally pushed by leaf springs toward the spring washers.
Also, the component parts of the first inclination angle adjusting mechanism and the second inclination angle adjusting mechanism may be formed from common parts except those components for the main shaft guide frame and the auxiliary shaft guide frame. As a result, the number of types of component parts is reduced, the cost is reduced and the component parts can be readily assembled.
Furthermore, in a preferred embodiment, the auxiliary shaft guide frame may have a pair of groove side surfaces that form the auxiliary shaft guide groove. The groove side surfaces may preferably have at least a section with a convex curved surface that protrudes from the groove side surface as viewed in the direction of the first axis. As a result, at least one of the groove side surfaces of the auxiliary shaft guide frame does not touch the auxiliary shaft when the inclination angle adjustment is performed about the first axis.
Moreover, in the second inclination angle adjusting mechanism, a distance between the center of the auxiliary shaft guide groove and the center of the second bearing shaft may preferably be set at a half or less than a distance between the center of the auxiliary shaft guide groove and the center of the main shaft. As a result, the amount of changes in the inclination angle of the auxiliary shaft guide frame, which is obtained by turning the second inclination angle adjusting screw, is smaller than the resultant amount of changes in the inclination angle of the main frame that mounts the objective lens. Accordingly, the resolution in the adjustment of the inclination angle can be increased as the difference in the distances is increased.
In accordance with another embodiment of the present invention, a method is provided for setting an objective lens of an optical pickup apparatus having the structure described above at a reference inclination angle position. The method is characterized in that first and second spacers each having predetermined thickness are interposed between the main frame and the respective main shaft guide frame and auxiliary shaft guide frame, and setting the main shaft guide frame and the auxiliary shaft guide frame at the reference inclination angle position with respect to the main frame.
By the optical pickup apparatus of the present invention in which the spacers are interposed in the manner described above, initial inclination angles about axes of the main frame, that are set when the main shaft guide frame and the auxiliary shaft guide frame are initially mounted on the main frame, can always be reproduced. As a result, if the performance of the head section deteriorates for one reason or another after the inclination angle of the head section is adjusted, the spacers are inserted, such that the performance of the head section can be evaluated in the same condition as that attained at factory before shipping of the optical pickup apparatus. Consequently, the determination and repair of defects can be readily performed.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, various features of embodiments of the invention.